ScienceDaily (July 13, 2010) — The efficacy of preimplantation genetic screening (PGS) has been one of the most hotly disputed subjects in assisted reproduction over the past few years. The European Society of Human Reproduction and Embryology (ESHRE) PGS Task Force has now shown, in its groundbreaking proof of principle study, that screening of polar bodies (small cells that are the by-product of egg development), is a reliable method to analyse the chromosomal status of an egg.